Nature and Nurture

The Big Questions How is evolution even possible, and what are genes, alleles, heritability, etc? How much of our behavior is genetic, and how much is environmental?

Humans developed from earlier species of animals A. True B. Not Sure C. False

Evolution? How does a fish EVER give birth to something other than a fish!?

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Hard to Fathom It took a long time (longer than you can imagine!) - very, very gradual change.. We don’t think of ourselves as cells: Is this from a fish or a human?? ?

Evolution and Lego

The same parts, reconfigured.. Evolution operates on an elaborate “instruction booklet” for constructing bodies from basic building blocks – the instruction book is subject to random and powerful hacking..

Fast Forward.. https://www.youtube.com/watch?v=z9ptOeB yLA4 (soft robots evolving before your eyes..)

The Instructions Genes = Lego instruction pages Base pair (G,C,T,A: Gattaca, nucleotide) 3 = one Lego brick (amino acid) Gene = Protein = sequence of amino acids (~300 = ~900 bp’s, but genes ~27,000 bp) Alleles = different instructions for different folks – different gene variants

The Instructions Genes = Lego instruction pages Only 1.5% of human DNA codes for proteins, ~20,000 proteins in all (like most animals) Between 20-85% of DNA may be “junk” Rest is regulatory / control: if, then, else, for, while, etc of the genetic program!

RNA and DNA DNA makes RNA (Transcription) RNA makes proteins (Translation) Proteins make us

98.8% Human? Proteins largely the same, but regulatory / junk areas differ by ~5%

Chromosomes etc 2x of everything: mom + dad = 2 Dominant vs. recessive: DD, Dr, rD, rr = ¾ dominant, ¼ rec. Chromosomes: in the nucleus of a cell, made up of DNA Dominant gene controls phenotype, recessive gene does not All the bad stuff is recessive: why incest is risky!

Genes and Behavior Genome-Wide Association Study (GWAS) for IQ: No single gene explains much, but if you put them all together, ~50% heritable. IQ = Phenotype Phenotype- observable characteristics or traits

Heritability h2 = proportion of variance explained by genetics Variance depends on the population you measure! h2 much higher in WEIRD populations (western, educated, industrialized, rich, democratic) because variance is lower! Why do you think variables like personality and social attitudes seem to be less heritable than these different disorders?

Behavioral Genetics is Big at CU http://www.colorado.edu/ibg/home The Colorado Adoption Project The Colorado Twin Registry The Colorado Learning Disabilities Research Center Twin study: compare monozygotic twins which share 100% of DNA, with dizygotic/fraternal twins that share 50% of DNA Allows them to estimate genetic basis of traits, as well as shared & unique environmental contributions

Were you a “geek” or a “nerd” in High School. A. Yes B. No C Were you a “geek” or a “nerd” in High School? A. Yes B. No C. Define “geek” / “nerd”..?

For the geeks / nerds Was this part of your “identity”, causing you to seek out other like-minded individuals, and pursue corresponding activities? A. Yes B. No C. Define “activities”..

Gene / Environment Correlations Overestimate heritability because genes influence environments! Geeks seeking geeks do geeky things together which makes them even geekier, and thus more likely to rule the world! And, yes, non-geeks shunning said geeks, further reinforcing said geekiness (reactive vs. active).

Everything is a Nature/Nurture Interaction Can’t be smart if you can’t eat. Deprivation of the basics leads to developmental problems no matter what genes you have Parents give you genes and, for most, your early environment (c.f., twins reared apart!) Brain is highly plastic (adaptive): h2 of IQ gets larger over time: it’s about learning!

Evolutionary Psychology Let me tell you a story about this caveman friend of mine.. Principles of evolutionary biology applied to human behavior: traits are evolutionary adaptations If you weren’t there, you don’t know what the real evolutionary forces were! (mostly “just so” stories / b.s.) Except really obvious things, like sex, violence (raping, pillaging: whose idea was that!?) Chimpanzees show same in-group / out-group behaviors as people.. Example: Infanticide- explained with evolutionary psychology- By stepfathers- not spending resources on children not related to reproductive success, children with low chance of success reduce mother’s genetic fitness, given the resources she spends on raising the child

Nature Nurture Summary Genes: made from DNA, determine how body develops (the program) Genotype = all genes; Alleles = different versions of gene Phenotype: measurable traits (IQ, ADHD..) Behavior(al) genetics: study of genetic vs. environment influence on behavior, etc Identical vs. fraternal twins vs. unrelated siblings Heritability (h2): amount of variance between people that is due to genes (0..1) (low variance = more h2) Almost everything has some heritability.. often ~.5

Nature Nurture Summary Environment: (shared = family, vs. unique) – everything outside of genes that affects you.. Everything (genes, environment) typically has an effect on everything.. e.g., IQ = 50/50 Gene / Environment Correlation: environment affected by genes.. (geeks!) Gene / Environment Interaction: different people respond differently to same environment

Evolutionary Psychology Summary Adaptations: changes to solve specific problems in the (old, evolutionary) environment Environmental mismatch: fat & sugar used to be good for you..  Sexual behavior, gender differences may be stronger targets for adaptations (double standards, etc)